This invention relates to a control mechanism for a bedroll of a rewinder.
Rewinders are used to convert large parent rolls of paper into retail sized rolls of bathroom tissue and paper towels. Two types of rewinders are commonly used--center rewinders and surface rewinders. Center rewinders are described, for example, in U. S. Reissue Pat. No. 28,353 and wind the web on a core which is rotated by a mandrel. Surface rewinders are described, for example, in U. S. Pat. Nos. 4,723,724 and 5,104,055 and wind the web on a core which is rotated by a three roll cradle.
The critical operation in both center rewinders and surface rewinders is the sequence of steps referred to as cutoff and transfer. The web must be severed to end the winding of one roll, the leading edge of the severed web must be transferred to a new core, and the new core must be rotated to begin winding a new roll. These steps must be accomplished repeatedly and reliably while the web is moving at high speed. It is also desirable that each roll have exact sheet count and that the web is wound uniformly and substantially without wrinkles.
The term "bedroll" refers to the main winding roll of a rewinder, either a center rewinder or a surface rewinder.
As described in U.S. Reissue Pat. No. 28,353, a bedroll is commonly used in conjunction with a chopper roll to sever the web after a predetermined length has been wound into a log and to transfer the leading edge of the severed web to a new core in a continuous winding process. In all current center rewinders a latch mechanism is used to retain the severing and transferring mechanism in an inoperative position until the proper length of web has been wound onto the log. A cam follower is controlled by an electric solenoid or pneumatic cylinder to unlatch the latch mechanism to release the severing and transferring mechanism. The severing and transferring mechanism is then controlled by one or more cams to perform the cutoff and transfer operations on the web. The latch is thereafter reset by the cam to retain the severing and transferring mechanism in the inoperative position.
A conventional latch mechanism and a severing and transferring mechanism for center rewinders is described in detail in U.S. Reissue Pat. No. 28,353. The severing and transfer mechanism includes pins 56, cutoff blades 58 and 59, and transfer pads 55, all of which are movably mounted in the bedroll. When the severing and transfer mechanism is unlatched, the pins 56 hold the web against the rotating bedroll while the web is severed by a chopper roll 49 and the blades 58 and 59 (see FIGS. 20 and 21). The transfer pads thereafter urge the leading end of the severed web against a new core 53 (FIGS. 22 and 23).
Surface rewinders sold by Paper Converting Machine Company of Green Bay, Wis. under the name "Magnum" include similar movable pins in a bedroll for holding the severed web against the bedroll and a similar latch mechanism for retaining the pins in an inoperative position until the web is to be severed. A cutoff knife is movably mounted in a chopper roll and is retained in an inoperative position by a latch mechanism which is similar to the latch mechanism which is used on the bedroll of a center rewinder.
One of the problems with the prior art severing and transfer mechanism is a limitation on the speed at which the solenoid can position the cam follower to release the latch mechanism. Another problem results from the impact loads on the components of the mechanism which cause fatigue failures and frequent maintenance. The mechanisms may also cause excessive vibration in the rewinder which can adversely affect other functions of the rewinder such as perforating the web.